X-ray tube



A. BOUWER$ K-RAY TUBE Jan. 10 1933.

Filed April 25. 192'? Patented Jan. 10, 1933 UNITED STATES PATENT OFFICE ALBERT BOUWERS, OF EINDHOVEN, NETHERLANDS, ASSIGNOR TO N. V. PHILIPS GIDEILAMPENFABRIEKEN, OI EINDHOVEN, NETHERLANDS, A LIMITED LIABILITY COMPANY OF THE NETHERLANDS X-BAY TUBE Application filed April 25, 1927, Serial No. 186,522, and in the Netherlands January 18, 1927.

The invention relates to X-ray tubes. lit is known that during the operation of an X-ray tube the anticathode becomes burnt in or is otherwise uniavorably affected when 5 the load of the focal spot exceeds a definite value.

Theoretically it can also be proved that with a determined anticathode material a given amount of energy must cause per unit of time a determined rise oi. temperature. A greater allowable load is obtained by constituting the anticathode of good heatconducting metal having a high melting point. Fundamentally, however, better results are obtained by mounting the anticathode so as to be movable.

For preventing the anticathode from becoming burnt in, it has been proposed to rotate the X-ray tube during its operation. In order to do this, the tube is enclosed at one of its ends in a clamping device mounted in an eccentric balhbearing, the other end of the tube being connected by a universal joint to a fixed point of support. When driven, the tube performs a certain conical oscillatingmovement and consequently the anticathode performs a circular movement in its plane. During operation, the cathode rays are concentrated by means of a set of magnets on the desired focal point. Such an installation is very complicated and the X-ray tube used therein has a short life.

According to the invention, it is possible to make use of a rotatable anticathode in such a manner that an X-ray tube suitable for practical use is produced, a result which has not been obtained hitherto. According to the invention, the anticathode of an X-ray tube having an outer wall which is partly of metal, is constructed so as to constitute the armature of an electric motor. According to a articular embodiment of the invention, t e anticathode is constructed as a rotor of an induction motor the stator of 5 which is located outside the tube, the Shell of the said motor being conductively connected to the metal wall portion of the tube, which portion is grounded.

According to the invention, the cathode can be eccentrically arranged in the tube. It is quite possible, however, to accomplish the same purpose by eccentrically disposing only the aperture of the focusing device, through which the cathode rays must pass.

The invention will be more clearly understood by referring to the accompanying drawing which diagrammatically represents one form of an X-ray tube according to the invention.

The glass portion of an X-ray tube is indicated at 1: 2 is a metal intermediate piece which preferably consists of chrome-iron be cause this alloy is not porous and can readily be sealed to glass.

The intermediate metal piece 2 is provided with a window 12 through which the active X-rays can emerge from the tube. 3 represents that portion of an anticathode which serves to intercept the cathode-rays and which is preferably made of tungsten. This tungsten portion is secured to a cylinder which terminates in a conical end surface the outer surface of which preferably consists of copper while the inner surface consists of a metal having a great permeability and which cylinder rests on ball-bearings 6 which permit the anticathode to rotate around a shaft 5 which may be hollow for the purpose of cooling. The anticathode constitutes the rotor of an induction motor, the stator of which consists of a magnet system 9 and a stator winding 11. In this mode of execution the shell 10 of the motor is connected to the metal intermediate piece 2 which is grounded. The anticathode preferably consists of a copper cylinder 8, which surrounds an inner cylinder 7 made of a metal having a great permeability, for instance of iron. An incandescent cathode 4 is directly connected at one of its ends to a is continually shifted with respect to the surface of the anticathode.

What I claim is: I

1. An X-ray tube having a cylindrically shaped outer envelope having mounted therein a cathode adapted to be heated to incandescence and a rotatable anticathode body, an electromagnetic stator for rotating said anticathode body mounted outside the tube, said anticathode body comprising an annular part located within the magnetic field of the said stator, said annular part comprising an outer copper portion surrounding and fixed to a form-magnetic cylinder.

2. An X-ray tube having a cylindrically shaped outer envelope enclosing a cathode adapted to be heated to incandescence, a focuss ng device surrounding said cathode and having an aperture for the passage of cathode rays, and an anticathode body, said anticathode body being rotatably mounted on a support. secured to the outer envelope centrally with respect to the tube, and means for rotating said anticathode body, said anticathode body terminat ng at the side turned to the cathode in a conical face, the aperture for the cathode rays in said focussing device being eccentrically arranged with respect to the axis of the tube.

3. As an element of an X-ray tube, an anticathode hody adapted to be used as the rotor of an induction motor and comprising an inner metal cylinder having a great magnetic permeability and an outer copper cylinder surrounding the inner cylinder.

4. As an element of an X-ray tube, a rotatable anti-cathode body comprising a cylinder of metal of great magnetic permeability, and a thin-walled copper cylinder closely surrounding said first-mentioned cylinder, and carrying a target of refractory metal.

5. An X-ray tube having an envelope, a cathode and. an anode therein. means to provide relative motion between the cathode and the anode, the said means comprising an electro-magnetic stator mounted exteriorly to the said envelope and adjacent the said anode, the said. anode having a tubular portion comprising an inner layer of iron and an outer layer of copper, a shaft arranged coaxially within said tube, and bearing elements between said shaft and said tubular portion, for the rotatable support of said anode.

6. An X-ray tube having a cylindrically shaped outer envelope consisting partly of metal and having mounted therein a cathode adapted to be heated to incandescence and a rotatable anticathode body, and means for providing relative motion etween said cathode and said anticathode body, said means comprising an electro-magnetic stator mounted outside the tube adjacent the anticathode body and conductively connected to the metal wall portion of the tube and forming together with the anticathode body and an induction motor, the anticathode body constituting the rotor of the motor and being for the greater part located in the magnetic field of said stator.

7 An X-ray tube having a cylindrically shaped outer envelope partly consisting of metal and enclosing a cathode adapted to be heated to incandescence and an anticathode body, said anticathode body being rotatably mounted on a support secured to the outer envelope centrally with respect to the tube, and comprising a head portion carrying a target and continuing at the side turned away from the cathode in an annular portion surrounding the said support, said tube having mcans for rotating the anticathode body, said means comprising an electric-magnetic stator mounted outside the tube adjacent the said annular portion of the anticathode body and conductively connected to the metallic wall portion of the tube and forming together with the anticathode body an induction motor, the rotor of which is constituted by the .anticathode body and comprises a magnetizable body.

8. An X-ray tube comprising an envelope, having mounted therein a cathode and an anticathode body disposed to rotate on the axis of the envelope, said anticathode body terminating in a front piece having a conical ray-emitting surface located opposite to said cathode, said cathode having an axis arranged eccentrically but substantially parallel with respect to the axis of the envelope, and means to continuously rotate the anticathode body.

9. An X-ray tube having an outer envelope, a cathode and an anode therein, means for providing relative motion between the cathode and the anode, the said means comprising an electro-magnetic stator, mounted exteriorly to the said outer envelope and adjacent the said anode, the said anode comprising a tubular cylindrical body formed of magnetically permeable material and having means defining portions of ball races therein, a second cylindrical-body encircling the first cylindrical body and having a target mounted in the end thereof adjacent the said cathode: and a supporting member surrounded. by said tubular cylindrical body of said anode, means on said member forming the inner portion of the ball races, and balls in said races.

10. As an element of an X-ra tube, an anticathode comprising a rotor an induction motor, and compnsing a magnetic portion surrounded by a. jacket formed of meterial of high electrical conductivity, and a. target of highly refractory metal carried thereby.

In testimon whereof I afiix my signature at the city 0 Eindhoven, this 29th day of March, 1927.

ALBERT BOU'WERS. 

